Among shaking machines, those which have shaking tables to be are shaken in circular orbital movements are each provided with a drive shaft, having at the upper end an eccentric shaft portion formed to have a predetermined off-center value, supported by a pair of bearings disposed to the top and bottom of a frame, with the eccentric shaft portion being fitted in a bearing attached to the lower surface of the shaking table. However, according to this constitution only, although the shaking table is caused to start a circular orbital revolving movement by the rotation of the drive shaft, it begins to autorotate before long to rotate integrally with the drive shaft and ceases shaking.
Accordingly, the above-described shaking machine is provided, at three or more positions around the drive shaft, with driven shafts each having an eccentric shaft portion with the same off-center value as in the counterpart in the drive shaft, and the eccentric shaft portions of the driven shafts are fitted not to the bearing described above but to other bearings attached to the lower surface of the shaking table, respectively, so that the eccentric shaft portions of the driven shafts may rotate in the same phase with respect to the eccentric shaft portion of the drive shaft to regulate autorotation of the shaking table and allow the shaking table to be shaken in a circular orbital revolving movement.
However, since this shaking machine uses one drive shaft and three or more driven shafts, all having eccentric shaft portions with the same off-center value, machining accuracy is strictly required in each shaft. Further, in order to obtain smooth shaking of the shaking table, phase adjustment accuracy is strictly required in the drive shaft and driven shafts in the step of assembling them. Accordingly, assembling and adjustment of the parts take time. Further, insufficient measures have been taken against vibration of the shaking machine itself caused by the eccentric movement of the shaking table.
It is an objective of the present invention to provide a shaking machine which can give smooth shaking of the shaking table using a simple structure and which can reduce the number of parts and the machining and assembling time, leading to reduction of its cost as a product and also vibration of the shaking machine itself.